


Changing Tides

by Jdragon122



Category: Supernatural
Genre: Caretaker Dean Winchester, Cecaelias, Creature Fic, Dean Winchester Whump, Eventual Smut, Fluff, Happy Ending, Hurt/Comfort, Interspecies Relationship(s), Interspecies Romance, Interspecies Sex, M/M, Mating Bites, Mer!Dean, Mer!Sam, Minor Violence, POV Castiel (Supernatural), POV Dean Winchester, POV Third Person Limited, Present Tense, Tentacle Sex, merfolk, mermaid au, octo!cas, shark!dean, shark!sam
Language: English
Status: Completed
Published: 2019-08-08
Updated: 2019-08-26
Packaged: 2020-08-11 11:35:18
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 17,488
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20152939
Author URL: https://archiveofourown.org/users/Jdragon122/pseuds/Jdragon122
Summary: Sam and Dean have lived on their own ever since Dean’s eighteenth cycle. Together, they hunt and survive. But when Sam gets hurt, its falls on Dean to pick up the slack and venture farther than he’s ever gone to get the food they need. Exploring a deep trench far from home, Dean finds something he’s only heard of in myths: a cecaelia. But this cecaelia is hurt. Curiosity and something more leads Dean to help the creature who calls himself Castiel. With the knowledge that Cas must eventually leave, they both grow closer but to what end?





	1. Chance Meeting

**Author's Note:**

  * For [destimushi](https://archiveofourown.org/users/destimushi/gifts).

> Hello everyone! Phew I've been sitting on this fic for a year but I've finally kicked my own butt and got it done! :D This was started as a fic for the lovely [destimushi](https://destimushi.tumblr.com/) whose [art](https://destimushi.tumblr.com/post/171242612883/wont-you-come-play-with-me-check-out-the) [work](https://destimushi.tumblr.com/post/171487679108/i-would-love-to-play-with-you-companion-piece) inspired this story! I adore any ocean-based anything so this was a fun one to write, even if it took me a while lol.  
And thank you to [ElleonOfOz](https://ellen-of-oz.tumblr.com/) for being so kind as to beta for me <3  
Without further ado! I hope you guys enjoy :)

The sea is dark, as it always is this late at night. The shimmer of fish overhead mimics the stars Dean so occasionally sees when he heads to the surface. He eyes the silver school as they swim together in a single harmonious body, unaware of his presence, his dark grey tail blending into the bottom of the depths.

With one strong sweep of his caudal fin, he speeds forward, ahead of the unsuspecting fish. He grips the carved whalebone blade in his hand and makes sure his kelp satchel is secured on his waist. Then, with a deep breath through his gills, he shoots upward.

The fish panic, as he knew they would, but with a practiced stroke of his blade, he slices the slowest of the group, downing three and swerving sharply. He lashes out with his tail, swinging as hard as he can as he turns. He feels several more fish against his fin, stunned by the blow and races after the rest of the group, teeth bared and claws outstretched. He snags one on his foreclaw and quickly bites its spine to end its wriggling.

Dean withdraws his fangs and watches what’s left of the school swim away. With a sigh he opens his satchel and tucks the fish into it. He swims around, collecting the rest of his prey, counting as he goes.

_ Four, five, six… aaand seven. _

He finishes counting, snapping the satchel shut. This should last him and Sam three days, maybe four if they stretch it out. He’d been trying to catch as much as he could for the both of them as they wander the ocean, to let Sam rest and heal. His stupid dork of a brother had injured his shoulder in a run-in with a group of extremely territorial tiger sharks. It’d been a scary situation at the time, causing Dean to jump in and fight off two while Sam took on the one. They’d both earned some more scars that day, but now, they could laugh about it.

_ How do _ ** _you _ ** _ get snuck up on by a tiger shark, you big whale? _Dean had chuckled.

_ I was busy looking for clams, Dean! _

_ Aw yes, to add to your shell collection, right? _

Sam smacked him with the tip of his tail, _ Shut up! _

A laugh hums in Dean’s chest at the memory. Oh poor Sammy, having to deal with his teasing for almost twenty-two cycles now. Dean is only two cycles older, but he still feels like both a parent and brother to Sam. It’s been a long time since their parents left, leaving them to fend for themselves as most all selachii do around their eighteenth cycle. But in this instance, Sam had done something Dean had never heard any other selachii siblings do. Dean had been to make his way in the world alone while Sam was to stay with their parents until his eighteenth cycle, but he made a choice, one that Dean will always be grateful for—he came with Dean. And so here they both are, exploring the oceans, together.

Being on their own isn’t easy. Sam knew the risks when he decided to leave with Dean, but Dean still feels guilt pool in his stomach whenever the food runs low and he watches the pained look on his brother’s face as the hunger sets in.

But Dean tries his best to never see that look on his face again. Of course, with Sam temporarily out of commission, things are more difficult. Which is why he’s spent every day for the past couple days doing nothing but hunting. They should be adequately stocked for the week, Dean thinks as he calculates their current storage. But it wouldn’t hurt to have a little extra.

Dean tucks the knife back in his belt, sweeping his faintly glowing eyes across the open sea. There are no other creatures in sight, he’ll have to look deeper. He lazily makes the dive down towards the darker waters. He doesn’t usually venture this far, but there is no risk without reward. He blows the air out of his gills as he reaches farther and farther into the dark, letting himself adjust to the pressure change. When he finally recognizes the walls of the trench, there is virtually no light left. But that’s no problem, Dean doesn’t need the light.

He scans the rock shelf, slowly sweeping his tail back and forth as he searches for the barnacles and anemone Sam is so fond of (_ You can’t just eat fish Dean! You need variety! _). He rolls his now fully glowing eyes. Sam and his picky eating, Dean never understood why he can’t just eat fish and crab like a normal selachii, but he still gets it for Sam when he can anyway.

He swims a bit longer, keeping in mind how far out he is now. He shouldn’t wander too far from Sam—the closer they are, the easier it is to rush back in case one of them is in danger. It’s that reminder that makes Dean sigh and slow his descent. As he’s about to turn around and head back up, a glowing patch of anemone catches his eye. He perks up, flapping his pectoral fins as he floats forward. He discovers the plantlife is farther than he’d expected.

The rock shelf delves deeper into the trench wall, opening up into a large cave system. Dean stares in awe as the rock hollows out into a long stretch of shimmering green crystal. The crystals are smooth, with cracks and vertical refractions of light embedded deep in their emerald depths, forming the walls and reflecting off his rough grey skin. Below him, Dean spots the misty surface of a brine pool and the smoke of vents billowing up to heat the cavern. It warms him from head to tail and sends a pleasant shiver through his body.

Dean can’t help but smile. It’s only every once in a while he or Sam come across beauty such as this. This was the one thing Dean likes about living out in the open ocean, never settling down—he gets to see the world. He swims further, nearly forgetting to grab the anemone, quickly ripping some off the walls. There is an abundance of it all throughout the system, growing in clusters around colonies of tube worms. Oh, Dean had hit the jackpot.

Dean grabs a couple more pieces of coral and anemone. They definitely have enough now, so Dean stops gathering, instead just wandering the cave. Dean’s never seen a cavern so large. It’s surprisingly light and Dean soon sees why when he spots the spread of bioluminescent wildlife bathing in the heat of the vents. It’s not often Dean dives deep enough to see such a sight, and this type of ecosystem seems to be closer to the surface than is typical. Too bad Sam isn’t here with him to see it.

Dean ventures deeper, skimming the pools below but making sure not to touch it. It still fascinates him how there can be lakes underwater.

_ I wonder what kelp Poseidon was on when he made these. _Dean laughs at his own joke. He brushes his hand against the smooth crystal, admiring how the light reflects off his claws. It almost matches his eyes, Dean thinks. He reluctantly turns away from it.

He takes a long breath through his nose, letting the scents wash over him. There’s the salt of the brine, the tang of the creatures floating along and then—he jolts as a strong wave of fear hits him.

The scent is prominent in the water, Dean is surprised he didn’t notice it sooner. It wafts towards him from a dark corner of the cavern, where a pocket is carved out of the wall. Dean approaches it slowly, scanning the dark for any movement. At first, he sees nothing, but then he notices the difference in texture. The wall of the little cave smooths out where there looks to be a small bundle. Dean approaches cautiously, nearing the strange object. Dean flinches back when the ball visibly tightens, trying to make itself as small as possible. Dean feels a horrible guilt weigh in his gut—it’s afraid of him.

_ Hey… hey, _ Dean hums soothingly into the water, _ It’s okay, I won’t hurt you. _

The ball shifts slightly, loosening enough that Dean catches a blue eye staring at him. That’s when Dean notices the tentacles. Previously the same green as the wall, now they shift to a darker blue. Dean gasps as the long arms lower to reveal the rest of the dark hair, pale torso and both of the stunning blue eyes.

Dean has heard of these creatures before, but only in myth. They are said to be very dangerous and extremely aggressive, with few who encountered them or their colonies coming back alive. But Dean can’t imagine the sight before him being anything less than beautiful.

_ You’re a cecaelia, right? _Dean asks. The cecaelia goes wide-eyed and nods slowly, still inching away from him.

_ Well I’m Dean, a selachii—if you couldn’t tell. _ Dean tries for a pleasant smile, but it doesn’t seem to help. Dean keeps trying. _ I’ve only ever heard of you guys, but I didn’t think you lived this deep—or alone. _

The cecaelia doesn’t respond, just stares, unblinking. Dean’s eyes skim the cecaelia’s body. He’s surprised when he notices the awkward way the cecaelia clutches his lower abdomen.

Dean frowns. _ You’re hurt. _He swims forward, hand raised. Dean stops immediately when the cecaelia’s tentacles flare a deep red and he rises up, teeth bared, frills and arms spreading. Dean goes wide-eyed and slowly backs away.

_ Okay, okay—I won’t touch. _Dean takes it back, he totally sees how they can be scary as shit. Once Dean's gotten over the obvious threat display, he sees that most of the cecaelia’s large appearance is due to the splay of tentacles, but the rest of his upper half looks dangerously thin. Dean knows this look—he mustn’t have eaten in a long while.

_ Um… here, _ Dean keeps eye contact as he slowly undoes his satchel and reaches into it. The cecaelia keeps track of his hand as it moves past his knife and into the bag. Dean takes out three fish and places them on the outcrop of the smaller cave. _ You look hungry. _

The cecaelia squints at the fish suspiciously. Dean just sighs, _ How would I have poisoned the fish when I didn’t even know you were here? _ The cecaelia still squints at him, but slowly reaches out an arm to grab all three fish and bring them into his lap. He gives Dean a nervous glance, but Dean just reassures him, _ Go ahead. _Without any further hesitation, the cecaelia picks up a fish and hastily sinks his teeth into it.

Dean watches him curiously as he devours the fish like he hasn’t eaten in days (which he might as well have). _ Hey, slow down… it’ll feel better that way. _The cecaelia glances up briefly before eating again, this time at a much slower pace. His tentacles slowly return to their blue hue as he deflates back onto the cave floor.

_ There, better? _

The cecaelia nods and continues to eat in silence. The other two fish quickly disappear, leaving only the scraps. Once it’s all gone, the cecaelia sinks even lower, eyes heavy, but still doesn’t remove the hand on his torso.

_ Is that why you haven’t eaten? _ Dean gestures to his side. _ You can’t hunt? _

The cecalia looks down at his hand then up at Dean. He nods solemnly.

_ And I’m guessing you can’t eat anemone. _

He nods again. Dean feels his heart sink. He and Sam have been through some rough patches but they always had each other to rely on should they get hurt. But out here, injured all on your own—you’re screwed.

_ Let me help you, _ Dean asks softly, tentatively raising his hand again. The cecalia’s arms ripple a deep purple but he doesn’t flare up again. Dean, unperturbed, swims forward and reaches for the cecaelia’s hand. _ Let me see. _ As soon as he brushes the cecaelia’s skin, arms fly out to enwrap him. Dean gasps as he’s suddenly pinned to the cave floor with a giant weight atop his chest. His hands are tied by the wrists and his tail immovable due to the unnaturally strong arms securing him in place. The cecaelia is above him now, bearing down on him, hissing with a full row of pointed teeth.

Dean shrivels back, trying to fight the feeling that he is very, very small. Dean curses as he smells his own fear in the water. He considers yelling for Sam, but there is no way Sam could reach him down here in time, even if Dean did put up a fight.

_ I’m sorry. _ Dean hates the way his vocals tremble slightly. _ I’ll leave you alone, I promise. And I-I’ve got a brother… he’s hurt and needs me to look out for him. I’ll give you some more fish, is that good? _

Dean is pleading and he knows and hates it. He prays that he hasn’t just made the biggest mistake of his life. Helping a cecaelia—he’s been warned of them, and yet he still didn’t take the hint.

The cecaelia stares at him, surprise filling his gaze. His grip starts to loosen but doesn’t let go altogether. Dean tries pushing against him but he stays put. All he can do is stare back and hope the cecaelia isn’t smart enough to know that Dean would last a lot longer than a couple fish.

Something must show on Dean’s face because the cecilia's expression changes. His curiosity melts into sadness. He meets Dean’s eyes for only a second more before dropping down. He lets go of Dean, drawing his arms back around himself in a hug. Dean darts out of the small cave as soon as he’s released, kicking up a small trail of sand. He only stops once he’s a safe distance away from the cecaelia. Dean stares at the cecaelia as he lays, once again, in a bundle on the floor, all aggression gone.

Dean can hear his heart pounding in his chest and he’s sure the cecaelia can too. But he’s not going to stick around to ask. Keeping to his word, Dean cautiously takes out another fish and places it on the edge of the cave. He glances one last time at the cecaelia, catching his big sparkling eyes before whirling around and racing out of the cavern.

He doesn’t stop swimming until he’s out of the trench and far past his usual hunting grounds. His heart is still racing like a rambunctious mako. He places a hand over his chest to try and calm it down and takes several deep breaths through his gills.

He could’ve died. He could’ve died and left Sammy alone and wondering what had happened. But he wasn’t dead, Dean reminds himself. It’s not like he’s never been in a life or death situation before, it’s just that it’s never been against another sentient creature. Of course, he’s wrestled with Sam plenty of times, but this is different. He shivers.

_ It’s okay, _ Dean hums to himself, _ You’ll go back to Sam, recount the food and act like none of this ever happened. It’ll all go back to normal. _

He drifts his way back to the Gleaming Rock where he and Sam have decided to take refuge. It’s nothing more than a tall shiny stone sticking out of the sand, fallen from the world above, but it’s full of strange and somewhat beautiful objects. Their favorite, though, is the reflection stone. The smooth, clear crystal surface shows a perfect replica of both Sam and Dean whenever they swim in front of it. It was the first time either of them had seen what they really looked like. It made Sam curious about the magic of the people above, but Dean just took what he was given and wondered nothing more.

Dean keeps going through old memories, calming himself until he finally spots their makeshift home. It slowly comes into focus as he nears and soon enough, he sees Sam’s head pop out from one of the circles in the rock.

_ You’re back! _ His little brother pushes the rest of his ridiculously long body through the circle and swims towards him. _ You took way longer this time. What was it? _

Dean swallows down his nervousness and smiles, reaching into his satchel. Sam gasps as Dean pulls out an anemone.

_ You found some?! _Sam’s face is enough to make Dean crack a genuine smile.

_ Yup, and there was a ton of it too! I had to dive pretty deep for these. _

_ You’re the best! _His brother draws him in for a bone-crushing hug. Dean feels the air squeezed out of his body as he reluctantly hugs back and groans.

_ Okay, you’re welcome… now could you—dude, you’re gonna hurt your shoulder again. _

_ Oh yeah. _ Sam releases him and glances down at his arm, covered in a kelp wrap where the bite wound lay underneath. _ But I think it’s getting better. _Sam smiles.

_ Good. _Dean smiles back. Sam glances him over and his face falls as he scans the length of Dean’s tail.

_ Wow, Dean… are you okay? _Dean frowns and looks down at his tail. He sucks in a sharp breath when he sees what Sam is staring at. Dark circles adorn a large area of his scales, protruding from where the cecaelia’s tentacles had latched onto him and stuck on hard enough to bruise.

_ Oh… _ Dean’s mind whirls until he finally comes up with an excuse, _ There was a giant octopus where the anemones were. Needless to say, he wasn’t too happy about me barging in there. _He cracks a smile which seems to fool Sam because he smiles back.

_ Just be more careful next time… don’t risk your life for some lousy plants. _

_ Oh, excuse me—who was the one going on about how healthy they are and judging me for my personal preference for the classic carnivorous diet? _

_ Just because I don’t agree with your eating habits doesn’t mean I want you to go wrestle a squid every time you go plant hunting. _

_ Octopus. _

_ Whatever. _Sam playfully ruffles his brother’s hair and swirls around before heading back inside.

_ Hey! I told you to stop doing that—I’m older than you! _

_ Well I’m bigger than you! _Sam calls over his shoulder. Dean huffs grumpily but just shakes his head as he follows Sam inside. Before he passes the threshold, he pauses. Dean looks back down at the bruises littering his tail then out towards the direction of the trench.

Now that Dean thinks about it, Dean can’t really blame the cecaelia for what he did. If Dean had been in the same situation, he would have probably done the same. A total stranger approaches you and gives you food, sure, but that can’t always be trusted. And then Dean had gone and touched him. That’s the line he shouldn’t have crossed. More guilt sinks onto his shoulders as he remembers the fear and hunger in his eyes. He was all alone, hurt and starving. Dean’s sure if he hadn’t fed him, he would only have a few more days before his body started to shut down—and it would be impossible to recover after that.

Dean will probably never know what will happen to the cecaelia. He’ll probably be gone by morning, having to relocate now that someone has found his hideout. Dean sighs. He wishes he had done more. But all he can do now is wish for the best and pray that wherever the cecaelia is, that he’ll be safe and comfortable and happy.

Whispering a quick prayer to the tides, Dean turns away and disappears into the cave.

**Notes for the Chapter:**

> Wooo that was chapter 1 everyone! :D this fic is finished so I'll be posting a chapter every Saturday! Thank you guys for reading! <3 I hope you've enjoyed it so far! And don't be afraid to shoot me a message over on [tumblr](https://jdragon122.tumblr.com/) ;)


	2. A Promise

**Summary for the Chapter:**

> Dean returns to the cave out of curiosity...

It’s been five days since Dean encountered the cecaelia down in the depths of the trench. He hasn’t thought much of it since—he has to keep thinking forward. No use dwelling on the past. He keeps up his usual routine; hunting, eating, sleeping, reapplying the paste to Sam’s shoulder and rewrapping it. Although the wound is far better than it had been, Sam has a long way to go before it’s fully healed. They will have to stay here for a couple more weeks—at least. Which means more hunting for Dean.

Most days, Dean is able to bring back a decent supply, but sometimes the fish just seem to disappear altogether, vanishing until a day or two later. It is rather frustrating.

Dean sighs as he swims along the same hunting path he’s been following for the past two weeks. He should probably scout out a new one soon—prey is becoming scarce and he has a feeling they’re catching on to his hunting pattern. But Dean doesn’t feel like exploring at the moment, scouting hunting grounds is a long and tiring task. Maybe tomorrow.

Dean continues on, swimming with the current and keeping his sense of smell and sight alert. An hour passes and still no prey reaches his senses. But Dean doesn’t stop, patience is a virtue he’s had to learn with practice.

He meanders along, humming to keep himself occupied. The ocean floor below him steeps downward and he pauses. He knows the trench is only a short way down. He hasn’t passed through this area since he’d been here the first time. He sends out a series of clicks to determine his location and finds that he’s slightly off course. He can easily correct himself but he doesn’t move.

There’s more anemone for him to gather if he returns to the cave. The cecaelia should be gone by now, it should be safe to go back. And if he’s not—well then he’ll deal with it if that happens.

He’ll be safe about it of course (Sam was constantly teasing him now about being suckered on by a cuddly octopus, and he didn’t need to add to his brother’s arsenal.) He just wanted to go see if the cecaelia was still there—and to grab some anemone.

Dean isn’t sure why he's so curious, but he feels the need to see if the cecaelia is gone and had gone on his way.

_ To see if he survived,  _ Dean thinks. He’s surprised at himself, that he’s so concerned about a creature that could (and almost did) kill him. But it wasn’t his fault, Dean reminds himself.

He considers turning around, continuing on his way, but his thoughts won’t leave him alone. When he tries to change course, his mind and body freezes, conflicted.

Finally, he groans,  _ Fuck it _ , and dives down into the trench. He can tell Sam it was for the anemone.

He swims down and down until his nocturnal vision kicks in. He follows along the rock wall until he begins to recognize the formation. He keeps going and inevitably finds what he’s looking for. The cave entrance is the same, and the plant life still glows from within the cavern, reflecting off the green crystals.

Dean approaches cautiously, slowly sweeping his tail back and forth. He breathes deeply as he enters, analyzing each scent that reaches his nose. He can’t smell the cecaelia, but he keeps himself alert. He passes the anemone, swimming towards the small cave hidden deeper in the cavern.

This is stupid, he knows. Sam will give him an earful if he finds out why he really returned here. He had been very clear about risking his life again. Why won’t he listen to reason?

He keeps going and sees the cave come into view. He smells the water again. The scent is faint, fading but not completely gone, just dampened. The closer he gets, he realizes, the stronger it becomes. His gills are on edge as he crawls forward.

_ Oh crap…  _ Dean stops, his mouth agape as he stares down at a motionless lump on the floor.  _ You poor stupid bastard.  _ He shoots forward to hover over the cecaelia, hands going to his shoulder to roll him over. He’s pale and thin, his ribs showing—and a long red gash runs from below his navel down across his lower half.  _ Why didn’t you let me help, you idiot… _

Dean sighs sadly, staring down at the cecaelia, his eyes closed and gaunt face relaxed, almost peaceful. He reaches down to place a hand next to his gills, to confirm what he knew.

He gasps when he feels the faintest rush of water. The cecaelia is, as impossible as it seems, alive—at least for now.  _ Oh shit, _ Dean grabs the cecaelia’s face between his hands. He situates himself to lie on the cave floor, placing the cecaelia’s head in his lap.  _ Hey, hey! Wake up!  _ Dean slaps his face a couple times.

The cecaelia’s eyes shift under his lids and his brow furrows as he grits his teeth and groans. It takes a few moments, the cecaelia shifting his body, curling in on himself, but eventually, he opens his eyes. The dazzling blue stares up at Dean, huge and full of desperation and again, fear. The surprise spreads across his face, as he stares up at Dean in shock.

_ Hey, hey. It’s okay,  _ Dean speaks softly,  _ I won’t hurt you.  _ The cecaelia shakes his head, confusion clouding his expression. His eyes dart around, his breath coming fast, face twisting in pain.  _ Don’t move, don’t move—I’ve got you, stay still.  _ Dean takes one hand from the cecaelia’s face and reaches down for his satchel.  _ You’re lucky I’ve got some of this with me. Forgot to put it back after I used it on Sammy.  _ Dean takes out a cockle shell, the two parts tied together with a length of seaweed. He undoes the string and puts one half down. He looks back down at the cecaelia, and freezes.

The cecaelia’s face has more emotion written on it than Dean had ever seen in another person. There’s appreciation, surprise, confusion, and something Dean can’t place. The cecaelia opens his mouth to speak but only a cough comes out. His body spasms and Dean rubs a comforting hand over his arm as it continues to rack his system.  _ Hey, don’t speak. Do that after you’ve got some nutrients in ya. Speaking of…  _ Dean reaches into the satchel again.  _ Here, have this—and remember, slow.  _ He places a fish in the cecaelia’s hand.

The relieved and heavenly look that passes over his face almost makes Dean chuckle if the situation weren’t as dire.  _ Here, hold on.  _ Dean gently pulls the cecaelia from under his arms over to the cave wall and leans him against it.  _ There, sitting up should make it easier.  _ The cecaelia doesn’t shift his gaze from him, still dumbfounded. Dean swallows and picks up the cockles shell again. He dips his fingers into the paste and pauses.  _ I’m gonna have to touch it. It will sting a bit. Promise you won’t go all cuttlefish on me again?  _ The cecaelia nods and raises a feeble hand to bring the fish to his mouth.  _ Good,  _ Dean swims closer to get a better look at the wound.

It’s a fairly deep cut, but clean, too clean.  _ This wasn’t an animal, was it? _ The cecaelia pauses momentarily but doesn’t respond.  _ It’s fine, you don’t have to tell me.  _ He carefully bends down, lightly applying the paste into the open wound. The cecaelia hisses, but lets him continue. He’s careful, soft with his touch as to not hurt him further with his claws.

They stay silent, Dean applying the paste while the cecaelia eats. His breathing is still quick and shallow, which heightens Dean’s worry. Dean clears his throat,  _ So… how long have you been here? How many days?  _ The cecaelia frowns for a moment, thinking. After a moment he raises his free hand. He splays all five fingers and opens and closes his hand three times.  _ 15 days?!  _ The cecaelia nods.  _ Did you even try to leave? Did you eat at all?!  _ The cecaelia shrinks back and Dean feels a twinge of guilt. He looks down at his lap and shakes his head. Then he lifts his eyes and points at Dean.  _ You didn’t try to leave…  _ The cecaelia nods,  _ and the last time you ate was when I came.  _ He nods again.  _ So what, you were gonna just lay down and die?  _ The cecaelia averts his eyes again. Dean sighs and shakes his head, drawing his hand back.  _ There… that should help it heal faster and not get infected. _

The cecaelia finishes eating then looks down at the wound. The greenish paste covers the majority of the injury, stopping the bleeding. He touches it tentatively, then tries to sit up further. He grimaces as the severed muscles stretch but is able to move himself into an upright position. Dean eyes him carefully, watching the way he shakes slightly.

_ You good?  _ Dean asks. The cecaelia nods immediately, his face red with effort. Dean chuckles,  _ You’re a horrible liar.  _ That earns him a dramatic eye roll.  _ Just don’t exert yourself too much.  _ The cecaelia’s tentacles ripple scarlet as he glares at him, but Dean just glares back, daring him to try something.  _ You ever heard the phrase, don’t bite the hand that feeds you?  _ The cecaelia tilts his head and squints. Dean huffs,  _ Yeah, that’s a good phrase to know. _ Dean swims next to the cecaelia and lies down, his chin resting on his arms and belly flat on the ground.

The cecaelia seems confused, his head tilting further as he stares at Dean on the floor. Dean stares back, eyes moving along the cecaelia’s form, curiosity sparkling in his eyes.  _ I uh… I’ve never really met a cecaelia before, you know. I only ever heard of you guys in scary stories to keep children in their caves at night. Merciless, strong, near-immortal—you guys are legendary. I never expected to find one and live… turns out I was wrong—though just barely…  _ The cecaelia looks down at the floor and picks at the gathered moss.  _ I’m sorry I didn’t listen to you,  _ Dean speaks softly,  _ I crossed a boundary and you had every right to defend yourself. That was my fault. _ The cecaelia looks surprised at this. Dean smiles to lighten the mood,  _ But I would appreciate if you don’t try and kill me again. _

The cecaelia looks down again, hands resting in his lap, tentacles curling inward.

_ Just be thankful I decided to come here. You look like you’d only have lasted a day or two more and then you’d be crab food, cecaelia. _

The cecaelia sighs, looking up to meet Dean's gaze. He opens his mouth, and Dean is surprised by the voice that he hears.

_ Castiel… my name is Castiel.  _ The cecaelia’s vocal frequency is deep and gruff, deeper than Dean's. Despite the roughness, his tone is warm and soothing to Dean’s ears, almost like a song. Dean sits up, eyes wide. He knew the people above spread tales of sirens and Dean thinks he understands why. If what they heard was anything like this...

_ Well it’s nice to finally get your name, Castiel.  _ Dean smiles at him.  _ And I’m— _

_ —Dean… I remember. _

Dean’s ear frills prick up in surprise at Castiel’s remembrance of his name.

_ It’s not easy to forget,  _ Castiel says, as if he’d read Dean’s mind.  _ I must thank you… _

Dean swallows nervously.  _ No problem…  _ Dean clears his throat.  _ So… do you think you’ll be okay? _

Castiel hugs himself, running his hand tentatively down his cut until the skin shifts to a dark blue.  _ I’ll be fine…  _ His voice is quiet.

Dean sighs. Another lie. Though Dean understands the need to hide weakness, that doesn’t mean he’ll leave him—again.  _ Don’t be stupid,  _ Dean huffs,  _ If I don’t come back you’ll die. _

Castiel’s eyes widen.  _ You’d… come back? _

_ You think I’d leave you here to die?  _ Dean asks. Castiel lowers his eyes and says nothing, restoring the silence between them. Dean swallows down his nervousness, pushing himself up into a sitting position with his tail laid out across the floor.  _ Ain’t gonna happen. _

There’s another pause, Castiel twisting his hands in his lap with his brow knit in confusion.  _ But… Dean,  _ He looks to Dean, blue eyes sparkling with curiosity and a hint of fear,  _ Why would you help me? A—aren’t you…  _

_ Scared of you? _

Cas looks away again, ashamed, playing with the end of one of his tentacles. He nods. Dean smirks a little as he watches Castiel, even if he does feel a little guilty about his amusement. This cecilia, as terrifying as the stories had made them seem, is nervous, if not scared—and rightfully so. Dean remembers the terror he’d felt in that moment when he’d been pinned to the ground. Of course he’d been scared, he’d been afraid for his life, and so had Castiel. That and all the stories had given him a preconception of what cecaelia were and what they did. How much of his initial fear had been from what he’d been taught and not from what he’d experienced? Are cecaelia really all that vicious and terrifying? And even if they are, how could Dean know if Castiel was like that too without getting a chance to know him? So far, the only thing he knows for sure is that Castiel is hurt, and if Dean doesn’t do anything to help, he will die.

Dean’s face softens, and for a moment he’s tempted to brush a comforting hand over the cecaelia’s arm, but thinks better of it. _ Was I afraid? Yes.  _ Castiel shrinks back a bit and Dean feels the guilt of it weigh on his heart.  _ But you’re hurt… and just as scared as I was.  _ Castiel’s eyes finally meet his again as he continues,  _ I’m helping you, Castiel, because…  _ Dean stops, trying to figure out the answer to his own explanation. And the truth would be he didn’t know, but instead he says,  _ Because I want to. _

The hard shell of Castiel’s expression cracks for a moment, softening to reveal the smallest hint of a smile. And unintentionally, he relaxes his arms, the blue brightening a few shades and uncurling onto the floor. Slowly, Castiel slinks forward, eyes still curious.

Dean is confused at first, but as Castiel nears, hand tentatively raised, Dean realizes what he’s doing. Castiel’s hand ghosts over the circular bruises still trailing down Dean’s tail. It sends a tingle down his skin to the tip of his fin.

_ Was this me? _

Dean nods wordlessly.

_ I’m sorry. I know you were just trying to help. _

_ It’s okay,  _ Dean says softly,  _ They’re almost healed anyway. _

Cas withdraws his hand and Dean lets the water flow out of his gills. The silence is no longer tense when Castiel leans back against the wall. Dean relaxes back onto the floor as he let’s Castiel’s eyes rove over the rest of his form. Then, to Dean's surprise, Castiel chuckles.

_ What, I look funny?  _ Dean smiles, letting the sound of laughter calm him.

_ No,  _ Castiel shakes his head,  _ it’s just—you seem so fascinated by my kind, but I’m just as curious about yours. _

Dean blinks, confused as to why a cecaelia would be curious about a creature as plain as him. At least Castiel is colorful—with his arms able to shift and swirl with an infinite array of hues and patterns, to shimmer and dazzle, and be  _ beautiful. _

It’s Dean’s turn to laugh,  _ Yeah not much to learn here buddy. But I guess if you’re cool with boring stuff, then a mutual exchange of information wouldn’t hurt. _

_ Don’t be so sure. I’m certain you have a very interesting story Dean. _

Dean blushes, picking at the stone floor and laughing nervously.  _ Well… I’d still like to hear yours.  _ He gestures to the gash on his torso.

The corner of Castiel’s lips dip into a frown, his small smile gone.  _ It’s… not a pleasant one. _

_ Neither is being attacked by sharks.  _ Dean gestures to the scars on his tail.  _ So spill. _

Castiel eyes the long white lines on Dean’s hide, obviously contemplating changing the subject but one look at Dean's face tells him he won’t be so easily distracted.  _ I was sentenced to death… _

Dean blinks, trying to process what he’d just heard.  _ What? _

_ I was to be executed. _

_ For what?  _ Dean’s mind cycles through all the horrible things Castiel could’ve done to deserve such a sentence.  _ What the hell did you do?! Kill someone?  _ Castiel struggles to speak, words catching in his throat.  _ Oh my Poisedon—you killed someone! _

_ No!  _ Castiel quickly says,  _ Quite the opposite! _

_ What do you mean?  _ Dean sweeps his tail, propelling himself up into the water, hovering.

_ I—I was… I disobeyed my orders.  _ Dean raises an eyebrow at him.  _ My mission was to annihilate a competing tribe… I couldn’t. I couldn’t do it. _

Dean blinks in confusion,  _ That’s it? Failing a mission is punishable by death? _

Castiel shakes his head, curling his tentacles more tightly than before.  _ No, it wasn’t just that… I refused outright. I told them what they were doing was wrong—that we could negotiate instead of wiping them out. I thought I could convince them but… my superiors saw it as treason… so they punished me accordingly—or tried to. _

Dean tries to wrap his head around what all the cecaelia is saying, but being a mostly solitary creature he can’t understand or know of the traditions of other species. It was never taught to him, he’d only heard stories. From what Castiel is saying, the stories got one thing right about cecaelia—they are a ruthless and largely military society. Though he can’t truly understand the thinking of such a cruel decision, he understands the harshness of being raised under strict rule.

_ There were children,  _ Cas continues as if Dean needs further evidence to convince him of his truthfulness,  _ Their colony was not unlike our own… I couldn’t bear the thought. On regular patrols or scouting missions it was defense, what they wanted was slaughter. I hope you can understand. _

_ Of course,  _ Dean nods sincerely,  _ If anything Castiel… I agree with you. You were brave speaking up and I can admire that. You chose the right way. _

_ Did I?  _ The cecaelia’s smile is genuine but it is tinged with sadness, _ But at what cost? _ He says, more to himself than to Dean.

Cas huffs a stream of bubbles from his gills but doesn’t continue. Dean stays silent, unsure how to respond to that. He can feel the tension in the water thick as a kelp forest. Worrying his bottom lip, Dean finally makes an attempt of encouragement.  _ Living alone isn’t all bad you know. _

Castiel looks up with an unconvinced frown on his face and eyes absolutely pitiful.  _ And how would you know? _

_ I live alone. _

Cas’s brow furrows.  _ You have no tribe? I’d have thought a specimen like you would be greatly desired. _

Dean blushes but the insinuation of the words seem completely lost on Cas.  _ Oh no, uh. My kind don’t live in tribes like yours? I wasn’t kicked out because I never had one to begin with. _

Cas looks shocked.  _ How do you survive? No tribemates to protect you or hunt for you if you're injured? How do you fend off the black behemoths in the winter? _

Dean shakes his head.  _ I live in warmer waters, behemoths are rare there. And I’m not completely alone. I have my brother. Even then, what me and Sam have is a special situation. _

_ Oh… so you’re not alone then.  _ Cas’s tentacles darken to a depressing blue. Dean sighs, swimming forward until he can rest his tail on the floor and shoulder on the rock wall. Arms crossed, he looks down at the cecaelia laying on the floor. The poor dude’s life had been ruined. Castiel had no plans for the future as was evident by the state Dean had found him in. An insistent nagging is forming in his chest, a protective instinct that’s growing by the second. He’d only come here to check on the cecaelia but a rapid plan is forming in his head that he definitely hadn’t approved of in his mental list of priorities. Poseidon, he really has so little impulse control.

Before Dean has fully processed what he was to say, his mouth blurts out,  _ And you won’t be either. _

Cas snaps his head up to meet his eyes,  _ What? _

Oh god, what was Dean thinking?  _ You heard me, you won’t be alone either. Like I said, I’m gonna keep visiting you till you’re all better. I’ll teach you how to do things on your own and when you’re strong enough, you'll be on your way.  _ Dean is already too attached. He’d promised to help him recover but now he’s offering to mentor him as well.

_ You don’t—  _ Cas’s voice is quiet _ , You don’t have to pity me. I can learn once I’m healed. You could even leave me some rations and the paste and you’d never have to bother with me again. _

_ Ah,  _ Dean points a finger at him,  _ Then how will I know you’re actually getting better instead of starving yourself? Just accept it, you’re stuck with me. _

Cas’s tentacles ripple purple in annoyance. Looks like Dean was right about that.  _ Does Sam know of this decision? _

Dean purses his lips,  _ No. And he doesn’t need to. _

Cas stares speechless, a guilty glint in his eyes.  _ Dean you needn’t do this— _

_ Yes—yes I do,  _ Dean’s jaw clenches,  _ I won’t let you die, Castiel, that I promise. _ There is a silence between them that Dean finalizes as he swims and picks up the cockle shell, wrapping it in seaweed again and placing it in his satchel. He takes a long breath through his gills.  _ I guess I should head back. Give me some more time to hunt before I go home. _

Castiel nods.  _ That would be wise. If you live in warm waters then the swim back must be long. _

Dean shrugs.  _ It’s fine. I’m used to it.  _ Dean knows he should leave but he can’t think how to properly end this conversation. Thankfully Cas seems to know how.

_ So… shall you tell me of your kind the next time we meet?  _

Dean’s lip curls in a small smile.

_ Course, gotta give you something to look forward to.  _ Dean smirks at him before swimming away slowly.  _ Oh!  _ Dean spins around and swims back suddenly.  _ Should probably leave you breakfast, it might be awhile.  _ Dean places another fish in Castiel’s hand and starts to pull away when the cecaelia covers his hand with his own. The deep blue of Castiel’s claws complement nicely the warm tan of Dean’s skin. Dean looks up and meets Castiel’s wide gaze.

The cecaelia smiles at him and whispers,  _ Thank you.  _ He squeezes Dean’s hand before releasing it. Dean has to shake himself from those eyes.

_ You’re welcome,  _ Dean feels himself blush as he looks away. He pulls back and starts towards the cavern entrance.  _ I’ll see you later, Cas. _ He swims a few feet before pausing, looking over his shoulder.  _ Is it okay if I call you Cas? _

Castiel ponders for a moment before nodding.  _ Yes. I think I like that name. _

_ Good.  _ Dean throws a smile his way.  _ Stay safe till I get back. _

_ I’m not going anywhere,  _ Cas states.

_ Okay, goodbye,  _ Dean waves at him, and Dean watches as the cecaelia awkwardly waves back.

_ Bye. _

Dean nods at him then swims out of the cave. As he ascends the trench, his mind buzzes, fins tingling with excitement. It’s been so long since he’s felt such a feeling, not since he was a young selachii, too young to know the destiny his parents would set for him once he came of age. Dean loves Sam with all his heart, but something new in his life makes it feel that much more of an adventure, one he can share with more than just Sam.

But Dean shouldn’t entertain such ideas. Once Cas is better, they’d part ways, likely never to see each other again. Dean swallows the sad thought. He will just live life as it comes and enjoy the moments he can and be grateful.

When Dean lies on the moss in his home late that night, he smiles. As far-fetched as the idea is, Dean hopes that he and Cas could grow to be friends, even if just for a short while. Knowing Cas is safe, Dean lets himself drift off to sleep and dream of soft, curling limbs and rippling blue.

**Notes for the Chapter:**

> Will be posting the next chapter next Saturday ;)  
And thank you everyone who's read, kudos'd, and commented! <3


	3. Deeper and Darker

**Summary for the Chapter:**

> Dean continues to visit Castiel but his most recent visit reminds him of the reality of their short friendship.

_ Heading out again today?  _ Sam rubs a hand over his sleepy eyes as he rolls off his bed of seamoss.

Dean looks over his shoulder as his brother blinks himself awake. _Yeah, of course._ _Can’t be slacking off when I’m hunting for two can I?_

_ You should let me come with you to help carry things at least. _

_ Naw, you’ll scare the fish away, you big whale.  _ Dean grins as Sam punches him playfully.  _ Come on. Be a good sport. The point of you lazing around is to get that shoulder of yours healed. _

Sam sighs,  _ Yeah, I guess, but you’ve been doing so much. It’s not fair, I should at least be pulling some weight. I could scour the sea bed for some more kelp, or clams near the shore— _

_ You pulling your tail around is fair enough Sammy. And you’re not going anywhere without me being there—buddy system, capiche? _

Sam snorts,  _ Hypocritical much? _

_ Well I’m older than you so… _

His brother folds his arms and raises an eyebrow at him,  _ Says the guy who was attacked by a cuttlefish. _

_ Octopus! _

_ Whatever.  _ Sam rolls his eyes.  _ All I’m saying is you don’t have to go out every day, you can relax, Dean. You’re doing more than enough. You keep hunting longer and longer. You’re barely making it back before nightfall now. _

Dean returns to his satchel, focusing on packing all the items he would need for the day. He clenches his jaw as he thinks of an excuse. He hates lying to Sam but it shouldn’t be too much longer.  _ Just trying to get the most I can out of the day. Besides, makes me feel productive. And you never know when the fish are gonna decide to vanish. _

Sam shakes his head, sweeping his tail to swim closer to his brother.  _ Dean,  _ Sam places a hand on his brother’s shoulder. Dean turns to face Sam with a questioning look.

_ What? _

Sam purses his lips.  _ Just make sure you’re staying safe … I don’t want to lose you. _

Dean smiles softly at the concern in his brother’s eyes.  _ It’s okay, Sammy,  _ he pats Sam’s arm assuringly,  _ I’ve got my knife, my charm, and a full row of pearly whites.  _ Dean’s smile widens to show off his sharp, pointed teeth. That earns Dean a playful shove as his brother turns away.

_ Well, there’s a lot of bigger fish with a lot of bigger teeth, so don’t get so cocky. _

_ Pssh, it’s not the size that matters. _

_ Shut up,  _ Sam smirks.  _ Well then, you go do your fishing and I’ll go take a sand bath. Which by the way, you need desperately, you’re starting to smell funny. _

Dean frowns and sniffs the water. He’d just taken one the day before. Though his scent was starting to mingle with Cas’s, but his brother not being familiar with the smell wouldn’t know any better.  _ Fine, after I come back tonight. At least I don’t smell like a clump of dead seaweed at the end of every day. _

_ I already told you, I have a high metabolism. Now go have fun killing things, jerk. _

_ Have fun smelling like dead fish, bitch.  _ They both laugh as Dean grabs his packed satchel and swims for the open ocean. Dean gives one last wave to his brother and shoots off towards the trench.

It’d been an entire two weeks since Dean had made his promise to Castiel, and he’s kept to that promise. Dean swims out every day to see the cecaelia, feed him, tend to his wound and just talk.

Castiel is an interesting fellow, Dean has come to learn—more than he’d anticipated. Once the cecaelia became more comfortable with him, their conversations became less about their different cultures and more about their individual lives. Dean learned that Castiel was raised as an extremely lethal warrior, had been the leader of a squadron in fact. All cecaelia children are raised to protect their tribe first. Castiel excelled due to his quick thinking and tendency for strategy. But his thinking got him in trouble sometimes; his strength was also his downfall. He’d question the status quo which led to many reprimandings and isolation from his fellow cecaelia. He did his job but when the day was done, Cas was alone.

He was a bit awkward, but once Dean got him to talk it was clear he was intelligent and thoughtful and extremely kind. Why no one would be his friend is beyond Dean. The guy might not have held conventional beliefs but he knows so much, there is so much he could talk about. Dean is fascinated by the knowledge Cas holds. All the years away from people were spent learning about the ocean and the history of his people written on stones on the outskirts of the tribe’s grounds.

Dean is enthralled. He’s never had anything like what Cas has. He’d sit for hours and do nothing but listen to the stories Cas had to tell. He learned things that’d he’d never in his life considered. How could anyone not yearn to hear the rumble of Cas’s voice and see the spark in his eyes as centuries of knowledge passed from his lips? Dean can only guess that in a society where the protection of the group was held to the extreme, Cas’s differing thoughts overshadowed every other personality trait he possesses.

Dean smiles at the memory of Cas’s tentacles curling and rings of color undulating across his many arms in excitement. Though there is a hint of sadness, knowing that no one had ever listened to Cas like Dean had, he was jealously happy that he got to be the first one to make Cas feel accepted.

Whenever it’s Dean’s time to talk, he feels he has nothing interesting to say. His life is simple; swimming across the open ocean with his parents, learning to survive so that when he came of age he might live long enough to find a mate and repeat the cycle. It’s dull compared to Cas’s tales of battle and grandeur. Dean’s life isn’t elegant, it’s dirty and brutal. Dean is lying if he said he isn’t jealous, even if Cas was an outcast.

Dean’s stories ended up being mostly of little Sammy, all the adventures he and his brother had had in their childhood and into adulthood. Though Dean never led battles he has his fair share of scars and showed them off with pride. He’d survived and that was one thing he could be proud of.

Cas is very curious about everything Dean has to tell him. He also has a tendency to touch Dean’s scars whenever Dean shares a new story behind them, especially if it had been a close call. It was like by touching them, he could take away the pain and trauma that came with them.

Despite the claws, Cas’s hands were soft and mesmerizing. Occasionally a tentacle or two would join, brushing over the spot protectively. When that happened, Dean would stop talking, too distracted and enamored to go on. It would last only a couple seconds, but in the small silence Dean could observe Cas, face bright with curiosity, unburdened by his past, so utterly focused on Dean that he felt warmth bleed into his heart and spread through him like steam through an ocean vent. Eventually, Cas would notice the silence and look to Dean, eyes catching in his gaze. Cas would blush, blue eyes apologetically wide as he backed away. He’d mutter an apology and politely ask Dean to continue his story.

Those moments were small and few but stick out in Dean’s memory. It always leaves him with an odd feeling, and he wondered if it does the same for Cas.

Today, Dean plans to tell Cas about when he saw the people from above. There are no scars to accompany this story, but it’s one of mystery that he thinks Cas would appreciate. Cas likes myths and legends so this seems up his current.

As Dean swims through the blue, sending out clicks to keep him on the right path, he keeps his senses alert for prey, or in the worst case, predators. There are no places to hide out in the open ocean, which is both to his advantage and disadvantage. But Dean is fast and agile, he’s wormed his way out of many nasty situations before and hasn’t failed yet.

Before Dean knows it, he senses the ocean floor dip below him. He follows the slope downward, letting the now-familiar rock formations guide him. The way is straightforward from there. Dive straight down until he sees the jutting rock then turn right.

He spots the cave with ease and picks up speed, a smile forming on his face.

_ Rise and shine sleepy head!  _ Dean calls as he barges into the cave, shooting straight for Cas’s spot. As suspected, the cecaelia is curled up in the corner, some tentacles nestled under him or hugged to his chest, head pillowed on another long arm. Lucky, Cas got to be his own blanket. It’s absolutely adorable.

_ Caaaaas, come on,  _ Dean circles above him, swirling the water and causing Cas’s hair to stick up. There is a soft growl from the now shifting mass of limbs.

_ Too much noise,  _ Cas grumbles.

Dean chuckles and stops his circles, leaning over Castiel with hands behind his back and a smirk on his face.  _ Okay, I’ll be quieter. But you should really get up, it’s almost mid-day. _

_ No, you’re lying,  _ Cas still refuses to move.

_ Oh no I’m not.  _ Cas simply sighs and Dean rolls his eyes. He lowers one hand and pokes the cecaelia in the shoulder. Dean knows Cas likes to sleep in, sometimes ridiculously long like now. But how could he blame him? The guy has almost nothing else to do during the day.

Dean continues to poke him in the shoulder,  _ If you wake up I’ll tell you another story while I check that nasty cut on your stomach.  _ Eventually, Cas growls again and his arms shift until Cas is completely covered in his own tentacle bubble.  _ Hey now, don’t be like that.  _ Dean pokes at his tentacles now, the funky things trying to twist out of his way. Finally, with one last poke a tentacles shoots out and grabs his wrist.  _ Hey!  _ Dean exclaims.

Slowly Cas sits up, the most grumpy and annoyed look on his face. He sighs,  _ I’ll get up if you would please stop. _

_ You know I would,  _ Dean grins,  _ but you kinda have me suckered here.  _ Dean lifts his enwrapped hand and shakes it.

Castiel gives Dean a bitchface that could rival even Sam’s. Dean just smiles wider as the tentacle releases him and curls back under Cas’s sleepy form. The cecaelia yawns, sharp teeth flashing and arms stretching outward, taking up almost the entire expanse of the small outcrop.

Dean watches, fascinated as his arms undulate with color from the tips of his tentacles to the edge of his webbing before retreating back to their curled state. Dean doesn’t notice Castiel watching him until he clears his throat and extends a demanding hand.

Dean shakes himself and stares at the cecaelia’s outstretched claws. Oh right, no talking until Cas has had his fish, that is his one rule. Dean smirks and reaches for his satchel. Obediently, he places the fish in Cas’s hand and the cecaelia sinks his teeth into it without a word.

Dean merely sits, amused, a bubbly joy warming his chest. When Cas is done, he sighs contently, the annoyance fading into bliss.

_ Better?  _ Dean chuckles.

_ Much. _

Dean can’t stop smiling, it seems automatic whenever he’s in Cas’s presence. He grows even happier when he looks Cas over and realizes that he can no longer see his ribs. They’d made good progress.

_ Alright,  _ Cas sighs, his mood significantly better,  _ Now what’s this story you promised me? _

Dean doesn’t hesitate, taking out the paste as he launches into his spiel.  _ Well did I ever tell you about the time I saw the people above? _

Cas’s eyes go wide,  _ You’ve seen them? _

Dean hums,  _ Mhm. Once when I was younger. I went up to the surface even though my dad told me not to. He was furious when he found out I did but hey I’m still alive aren’t I? _

_ Thankfully so,  _ Cas graces him with one of his soft half-smiles. It makes Dean heart swim. He carefully starts peeling Castiel’s bandage off as he continues.

_ I’d never seen above the water before so the dumb selachii that I was thought I’d swim up and see for myself. When I got there… you wouldn’t believe it, Cas, I’d never seen anything like it. _

Cas’s eyes widen as he listens with rapt attention.

_ The ocean ended Cas, it just stopped. There’s no water up there, just this strange current. It’s like there’s a barrier between the ocean and the beyond.  _ Dean gestures dramatically towards the cavern ceiling, letting his voice rise and fall. _ You can’t breathe up there either but if you look up you’ll see this other ocean, just as blue as ours but instead of fish swimming in it there are these huge white beasts! _

Dean watches Cas’s face, soaking in the sparkle in his eyes and the curl of his lips.  _ Do the people above fear these beasts? _

_ I don’t know,  _ Dean shakes his head,  _ But they’re everywhere. Maybe they don’t eat them. Anyway _ — Dean focuses back on the bandage.  _ I was so focused on what I saw that I didn’t notice this strange brown thing coming towards me. _

Castiel gasps and Dean can’t help but laugh.  _ When I looked I saw it was the people from above, two of them sitting in the thing and floating on top of the water. They looked almost like us, Cas. They had the same torsos, arms, and faces, but they had no tails. _

_ How do they swim around?  _ Cas furrows his brow.

_ It was really weird, it looked like they had two tails but they didn’t swim with them. It was like their fins kept sticking to their floating thing. Like your arms! _

_ How peculiar,  _ the cecaelia hums,  _ Did they see you? _

Dean pauses for a moment, a frown forming on his face. He’s peeled the bandage almost half way off but he can’t seem to see the wound.

_ No,  _ he continues, trying to keep the excitement in his voice,  _ Not at first. I ducked back under the water but they must’ve heard me. I stayed under but…  _ He trails off.

Dean stops.

Castiel stares at him with concern,  _ Dean what’s wrong?  _ Cas follows Dean’s gaze down to the wound. Dean’s hands twitch nervously as he hovers over the last of the bandage. They both stare with bated breath.

Dean rips the rest of it off and sees what he’s been dreading for a long time. The wound has fully healed.

They both sit, not moving or speaking, their warm moment dropping dead as the realization falls upon them both.

Dean feels his mouth go dry, as if he’s swallowed a lump of salt, but he has to say something.  _ You’re… you’re healed.  _ He looks up and is met with a sadness Dean wished to never see on the cecaelia’s face ever again.

Cas is all better now. He could survive on his own again. He doesn’t need feeding or caudling anymore—he doesn’t need Dean.

Dean swallows.  _ So… you’re all better. That’s awesome. It’ll be a relief to finally be out of this cave huh?  _ He forces himself to smile but it does little to change Cas’s expression.

_ Dean, I _ —

_ No,  _ Dean continues to smile but it doesn’t reach his eyes.  _ It’s alright, Cas. I’m happy for you. This is why I stayed, isn’t it? To give you your freedom again. Don’t worry about me, you’ll get to go live your life again. _

Cas opens his mouth but closes it again, averting his eyes to the cave floor. Dean tentatively touches the healed skin, scarred but smooth. He sees Cas watching him out of the corner of his eye but he can’t seem to pull away.

A hand wraps around Dean’s own, pulling it away and holding it between them. Dean meets Castiel’s gaze and finds it warm and comforting, a sad smile on his face.  _ Dean…  _ He keeps a hold of Dean’s hand, rubbing soothing circles on his skin.  _ Thank you. I haven’t met a kinder soul in all my years… _

No. Dean can’t do goodbyes right now, not so soon.  _ Hey,  _ Dean interrupts him,  _ Let’s not… Let’s not do that right now, okay? _

Cas again looks like he wants to say more but keeps his mouth closed.

_ Tomorrow I’ll come see you off but for now… how ‘bout I finish the story?  _ Even as Dean sings the words they feel sour in his throat.

Castiel’s eyes fill with more sadness and what Dean hopes is longing, but he’s not one to hold onto hope.

_ I…  _ Cas’s voice is quiet,  _ I’d like that. _

Dean flashes him another false grin but this one seems to work, the slightest pull of a smile curling the cecaelia’s lips.  _ Alright.  _ He stares for a moment longer, a deep sorrow embedding itself in Dean’s heart. If this is the last time Dean gets to be with Cas, he’s going to make it count. His memories will be happy and filled with joy, as they should be.

_ So they started looking over into the water and I managed to swim under their floating island, but they must’ve seen my tail. They started yelling at each other. The way they talk isn’t like us. It’s rough and ugly, no wonder they like our voices better— _

Dean keeps rambling on, ignoring the gloom hanging over every word. Cas plays along too, the both of them trying to return to normalcy despite what they know is coming. It seems to help as Dean goes on and on. They talk, they laugh, like they would any other day. But when the day begins to wane and Dean eventually must go, their goodbyes are soft, tender. It takes everything for Dean to turn around and swim away, knowing that Cas watches as he disappears, knowing that after the next day he would never see Castiel ever again.

When Dean heads out the next morning, it doesn’t feel like he thought it would. He’s known ever since he’d started taking care of Cas that he would eventually have to leave. He knew it in his mind, but he couldn’t seem to accept it in his heart.

As he swims out to the trench for the last time, his movements are slow and lethargic. Dean is dragging his tail and he knew it. Maybe, he thought, if he prolonged the inevitable that when he got to Cas, he’d know just what to say, how to say goodbye. He’d likely never see him again, the ocean was too big, the chances too small. He’s only got one shot at this, then he’ll be gone forever.

He tries to play out the conversation in his head, but it hurts every time he does. Dean sighs, he should be content and simply grateful he was lucky enough to come across the cecaelia in his lifetime. It’s these short moments that make this hard life worth living.

Dean clicks a couple times to grasp his bearings. He doesn’t bother trying to be too quiet, he doesn’t feel like hunting today. The seabed still lies flat, the trench a little ways away. The closer he gets the more of a sinking feeling he gets, but he shouldn't wait too long. Cas might start to worry.

Dean picks up the pace, beating his tail back and forth monotonously. Time passes until Dean finally notices the sea below him begin to darken. He clicks again and sure enough, the trench is directly below him.

He prepares to dive when he’s surprised by another one of his echoes bouncing back at him far too quickly. Dean frowns, looking towards the direction of the sound. He sends out another click and sure enough, it echoes back at him, closer this time. Dean frowns, his senses once again alert as he strains to see in front of him. His night vision sets in and he sees a large blob against the background of blue.

Whales weren’t uncommon out here, Dean had swum with a couple but they usually echoed back at him with a friendly hello. As it slowly got larger, Dean begins to get a feeling that rubbed his scales the wrong way. He immediately stops clicking and begins to descend, trying not to stir up too much water.

As Dean stares at the growing mass, his heart sinks as it grows darker and another shape appears beside it. The creature grows clearer and clearer until Dean could recognize the rounded pectoral fins and white that surrounded its beady eyes.

_ Shit! _ Dean dives immediately, beating his tail as hard as he could. Dammit, he got lazy one fucking time! What are behemoths even doing this deep at this time of the season? They almost never come around these parts.

Adrenaline begins to pump through his system as he hears the clicks of the whales sound around him. They know they’d been spotted and were moving in. It’s useless to be silent now. Dean lets out more clicks, trying to gauge how far he has to sprint and how many more whales are undoubtedly around him.

Sure enough, Dean hears more clicks around him, the pod’s communicating disorientingly loud. How could he have been so stupid?!

_ Fuck, fuck,  _ Dean mutters frantically as he folds his arms in front of him, trying to cut quicker through the water. He needs to hide, he needs to dive deep enough and find somewhere to hide. Shit, he hopes Cas is still safe in his cave.

Dean suddenly rears up, heart in his throat as a giant bulbous head appears from the darkness towards him, almost running straight into him. It swerves at the last second, pushing him upward with its tail.

Dean curses himself for stopping instead of dodging, his speed significantly slowed. He beats his tail, shooting diagonally downward and under the beast. Two more behemoths appear from below, blocking his way down.

Dean knows behemoths are smart, but he never realized just how dangerous their teamwork could be. He has no choice but to go up again.

He clicks again and to his horror senses them surrounding him on all sides. They are funneling him where they want him to go, and there’s nothing he can do.

Dean knows he will probably never be heard but he calls in desperation, pleading to anyone that would listen, a loud, high-pitched series of close clicks.

Dean keeps swimming, trying to worm around as best he can. He squeals as he feels one poke him on his side, grabbing ahold of his satchel and thrashing it around. He tears the bag off, rushing over the behemoth while it’s occupied, only to feel sharp teeth latch onto his dorsal fin.

Dean screams, clawing behind him to scratch at the beast the best he can. No, no, no—he doesn’t want this to be the end. He smells his blood in the water as the behemoth shakes him, teeth sinking in deeper until it finally lets go.

He sprints down, making a mad dash for the trench. Fear claws at him, water rushing through his gills. He can’t leave Sam and Cas, they need him, he promised to take care of them.

The behemoths squeak with glee as he tries to escape. He understands their celebrating when once again one of the beasts appear from the darkness, but this time it doesn’t swerve.

It crashes right into him, ripping the water from his gills. Dean feels his teeth grind against his jaw, his stunned body useless to move as he is dragged back into the death circle. He feels himself sink as the beast lets him go. His vision blurs, mind numb. It’s over, he thinks sadly. At least he met Cas, and Sam is strong enough to survive without him. He’s done his part.

There’s nothing left he can do.

Dean closes his eyes and lets himself fade.

Castiel waits. He twists a tentacle in his hand nervously, stomach in a knot. He lies against the wall, as he’s gotten used to over the past weeks. Today is the day he’ll be on his own again.

Cas turns on his side and curls up tighter at the thought. Getting to know Dean has opened his eyes to a world outside of cecaelia society. It’s strange, how much one person has changed him. He expected to die and had accepted that fact, but Dean changed that… Dean saved him.

Cas wishes he didn’t have to leave. He is surprised at himself but it’s the truth. Where had he to go? What had he to do? He’d be on his own. Dean is the only person who’d showed him true compassion. Compared to his own kind, Cas realizes, Dean is warm and caring and loving. Dean had never known him, Cas had attacked him, and yet he stayed. Letting him go would be one of the hardest things he’d ever have to do.

The cecaelia tries to focus on something else, but his mind seems anchored to the anxiety plaguing him. All he could think of were green eyes and gray scales, it was all he’d had—it was all he  _ has  _ without his fellow cecaelia. He doesn’t know what to do.

Cas presses a hand over where the scar from the spear that cut him sits, slowly fading. He almost wishes it was still there. He is being stupid, he knows. Dean is a stranger, no matter how close he thought they’d gotten over less than a month of knowing each other. Dean had been kind enough to put up with him and his stories, but Dean owes him nothing. Cas owes him everything, which is why he will leave.

Castiel sighs, a stream of bubbles drifting to the ceiling as his tentacles shift to black with circles of blue. Shifting is all he can really do to pass the time, which is drawing out longer than expected. He’s able to judge the time Dean usually arrives, his internal clock still working properly despite the lack of light. Dean is taking longer than usual today. Cas frowns, maybe he is just late.

Castiel picks at the moss of the cave wall, waiting. Then, out of curiosity, he smells the water. A faint but familiar scent fills his nose. Castiel’s eyes go wide, his body instinctively backing to the farthest corner of the cave. He knows that smell anywhere. Behemoths.

Judging by the size of the cave entrance, Cas should be safe, he reasons. They wouldn’t fit even if they did sense him. He relaxes slightly until another thought hits him.

Dean is out there, swimming towards him—straight towards the behemoths.

_ Oh no, oh no,  _ Cas mutters, biting his claws as he swims back and forth. No, they couldn’t get Dean. This is all his fault. He has to go make sure he is okay. He knows roughly where Dean would be coming from, he should go check.

Cas takes a deep breath, trying to calm himself. Dean is smart enough, he’d know to lie low when he smelled them… right? Cas remembers Dean telling him that he’d never run into the behemoths before, which meant that Dean wouldn’t know what they smell like.

Panic steadily fills him. Cas knows he can’t just stay here, he has to be sure Dean is alright. Gathering his courage, Cas makes his way towards the opening. He pokes his head out, letting his eyes adjust and sniffing the water. The scent of behemoths is definitely strong. He looks around, seeing nothing in the darkness. Faint light shines from above, but nothing else shows.

Cas listens intently, waiting for any movement, but there isn’t any. Cautiously, Cas emerges from the cave for the first time in weeks. Despite having continued working himself during his injury as any warrior would, his limbs feel weaker in the open water. He keeps himself close to the trench wall, ready to dash back at any moment. This could be stupid. He could be risking himself for no reason. Dean is probably fine, but he can’t shake the feeling.

The cecaelia adjusts his tentacles, matching them to the color and texture of the rock wall as he steadily ascends, senses alert. A strong wave of water pushes him towards the rocks and Cas shrinks against it as the smell of behemoth wafts with it. He watches as a huge black mass with streaks of white barrels past him, making its way towards the surface. Cas looks up, intent on what it is looking for. He sees nothing, but hears the clicks of several of the beasts slowly echoing through the water. They found something, he knows the pattern of their noise well enough to know, but what was it?

A dot appears over the lip of the trench, growing slowly larger as it descends at a rapid pace. Cas squints to try and make out what it is. He can’t yet smell what it is, its scent still making its way through the tide but it is clearly and reasonably panicked. It looks like a shark, making its way right in the ascending behemoths direction. Cas watches with heart in his throat as the beast swims towards it. It almost runs straight into it, causing the poor creature to rear away sharply. As it veers away, Cas finally sees the upper torso, arms scrambling and the horror dawns on him. It’s Dean.

_ Dean!  _ He cries, abandoning all stealth and rushing as fast as he could towards the selachii, pushing water through his siphons rapidly. He is still very far from Dean. He watches as the other behemoths appear and Cas nearly cries again as he sees Dean trying to escape, the beasts biting at him, Dean maneuvering and calling out until one of them grabs hold of his fin. The scream that pierces the water shakes Castiel to the bone.  _ DEAN! DEAN!  _ He screams again, the plea escaping him automatically.

The behemoth thrashes Dean around, filling the water with blood. Cas sprints harder, muscles burning as he grows closer and closer but it might be too late. It lets Dean go, allowing him to try and escape one last time. Cas sees it coming, he knows Dean is too disoriented to sense it. Another behemoth rises from the depths, laying in wait for the right moment and charges right into him.

Cas is close enough now to see the shock on Dean’s face before it hits. There’s a loud thud when the beast collides, Dean’s body tenses as he’s dragged back up but doesn’t fight. The behemoth swerves away, letting Dean go. Cas calls out again, hoping Dean can hear him this time, but it’s clear from Dean’s limpness that he’s either too late or about to be.

The circle of behemoths are all focused on Dean, not paying attention to the small creature charging towards them. Cas is so close, just a little farther, he has to push harder. Cas’s muscles scream at him as he tries to swim faster and faster as the beasts close in.

Rage fills Castiel as he listens to their clicks of triumph,  _ You—will not—HAVE HIM!  _ Cas bursts through the middle of them, grabbing onto Dean’s limp body. Cas veers himself around and sprints, spraying a pool of black ink behind him as he goes.

He hears the sound of confusion as the beasts try and see through the black. It only gives Castiel a couple of seconds but it is a precious few seconds. By the time Cas hears the behemoths following suit, he’s already passed the trench lip and is pushing his way down. With the added weight of Dean, Cas can’t swim as fast as he could and Cas realizes this as he feels the rush of water from the behemoths behind him. At this pace, he’ll never make it back to the cave.

_ Dean, please wake up! _ Cas squeezes even tighter under Dean’s arms but he doesn’t respond. Fuck.

Cas risks a look behind him and goes wide eyed when he sees a behemoth barely an arms’ length behind him. He is definitely not making it to the cave. Thinking quickly, Cas scans the trench wall ahead of him as he sprints, looking for any cover or formation. His eyes latch onto an indent he sees a couple meters away. It might not have enough cover for them to escape or it might. Cas would just have to pray the gods were in his favor.

Cas can feel the vibrations in the water as the behemoth gets closer, his tentacles almost touching its snout.  _ Oh gods please.  _ The indent is right up ahead. He braces himself as he judges the distance then flares out his arms and shoots to the side. His tentacles brush the behemoth’s flank as it dives past them, unable to maneuver so quickly. Cas scrambles on the rock wall and pushes himself and Dean as tightly behind the rock formation as he can, tangling his arms around Dean and covering them both in a disguise of camouflaged tentacles.

Cas is shaking, breath coming fast, with nothing else he can do but wait. One hand gripping Dean and the other over his mouth to try and quiet himself, Cas closes his eyes and curls as tightly as he can.

There’s a thud against the rock and Cas’s eyes fly open to the crevice he’d squeezed through. Through it he could see the head of a behemoth, bumping against the entrance, trying to get through. It tries a couple more times, knocking against the rock until it finally gives up. It gives a long, dissatisfied click and turns away, leaving an eerie silence as it faded back into the darkness.

Cas lets out a long breath, letting himself breathe properly as his mind begins to settle. They are safe. It is okay now, they’re safe. Cas looks down at Dean in his arms, his friend still unconscious.  _ Dean?  _ Cas adjusts him so that he can cradle him against his chest. He cups a hand over his cheek and tilts his face towards him.  _ Dean.  _ Cas shakes him.  _ It’s okay now. You’re safe… you’re safe.  _ Dean stirs slightly and Cas’s attention is on him immediately.  _ Dean? Dean! Come on wake up. _ The selachii’s brow furrows, teeth gritted. Then, very slowly, his eyes open.

Dean blinks several times, his gaze unfocused until he lands on Cas.  _ Cas?  _ Dean frowns,  _ What… why are you— _ Dean groans and leans his head against Cas’s chest.  _ My head and my fin… it hurts. _

_ I know, I know,  _ Cas coos and rubs his thumb against Dean’s cheek.

_ Where are the behemoths? Are we dead? _

_ No,  _ Cas chuckles sadly,  _ No… I saved you. You’re okay. _

_ You did? How? _

Cas smiles down at him,  _ I saw them chasing you and hurting you. I swam as fast as I could. I managed to grab you after it rammed into you. Then I swam us here and they left. _

Dean squints up at him, finally seeming to notice how close they are, Cas’s tentacles caressing him softly and the hand on his cheek.  _ You saved me…  _ he whispers. Cas nods. Dean searches his face and whatever he’s looking for he must find because he smiles, a small but pleasant thing.

Dean starts to shake in his arms and Cas adjusts to hug him with both arms. Slowly, Dean returns the gesture, arms slowly wrapping around Cas and staying there.

_ Thank you…  _ Dean mutters brokenly into his shoulder. Cas smooths a hand down his back, careful to avoid the bite marks.

_ You’re welcome Dean… I’m glad you’re okay.  _ Dean is properly shivering now. Cas recognizes the shock of the battle settling in, his body still dazed.  _ Rest Dean,  _ Cas whispers,  _ I’ll wake you when I can’t smell them anymore.  _ Without a word, Dean hesitantly buries his face in Cas’s neck, cheek resting against his shoulder. Cas closes his eyes and leans his head onto Dean, tentacles stroking slow soothing patterns onto his tail.

They stay there, wrapped in each other as Cas waits. He continues to smell the water, waiting for the scent to fade and the behemoths to be gone. But until then, he hugs Dean to his chest, eyes closed and lets himself enjoy the warmth of the body next to him.


	4. Safe to Start Again

**Summary for the Chapter:**

> Cas and Dean return safely to the cave - but now they must decide what to do next.

**Notes for the Chapter:**

> Ah hello! Sorry for the slight delay of this last chapter. School just started back up for me so that had to take priority for a little bit. But alas, here it is! Enjoy ;)

When Cas finally deems it safe to return to the cave, the day has already begun to wilt away. Cas waits for a few hours just to be certain, but he doesn’t want to make Dean stay any longer in his condition. They quietly make their way back, Cas keeping hold of Dean to guide him along.

Dean hisses every now and again if he moves his tail too much. Cas simply pulls him a little closer and lets Dean glide alongside him, no effort needed on his part. Dean had stopped bleeding a while back, for which Cas is thankful. Without Dean’s salve there is nothing Cas has to stop it on his own.

As soon as they make it back, Cas leads Dean to the outcrop where he had lain not hours before. Dean settles onto his belly as soon as he reaches the cave, his tail stretched out and caudal fin resting sideways on the rock, face hidden against his folded arms. He sighs and Cas can’t help but brush a tentacle across his tail as he passes, settling between Dean and the wall.

Cas observes the damage as Dean does nothing but breathe steadily through his gills, his chest rising and falling. There’s bruising on Dean’s side where the behemoth rammed him, and his dorsal fin had a ring of fresh teeth marks that are red and raw. They’re sure to leave a scar, no doubt, but at least Dean will have another story to tell.

Cas lets Dean lie there, guilt finally allowing itself to trickle its way into his heart. He bites his bottom lip and twirls one of his tentacles, trying to keep the burning from his eyes. Dean almost died. Dean was coming here to see him and almost died. Gods, he should’ve never let this happen.

Cas swallows and slowly approaches the selachii, words stuck on the tip of his tongue. Dean shifts slightly, his tail scraping the floor as he reluctantly takes a heavy breath and pushes himself up on one elbow, the other resting across his torso. He tenses as his dorsal fin touches the floor but grits his teeth and raises his head to look at Cas.

Castiel pauses, hovering in front of Dean, searching his face for any hint of anger. He sees none. Maybe he isn’t looking right. Cas looks down at his hands, unable to meet Dean’s gaze any longer.  _ Um, how do you feel? _

Cas hears Dean move.  _ Better than I was,  _ Dean’s song is soft, not as strong as before but solid,  _ thanks to you. _ Cas gasps as he feels Dean’s hand slide over his, anchoring him, the fact that they were both alive.

The cecaelia is forced to look up, fingers tilting his head.  _ Hey,  _ Dean’s hum is soothing,  _ It’s not your fault okay? Stop looking like that. It wasn’t you. _

_ But—But you came for me. If you hadn’t it would’ve all been fine. You’d wouldn’t be hurt. You wouldn’t have almost  _ ** _died_ ** _ . _

_ Shhh, I came because I’m your friend. I wasn’t gonna let you leave without saying goodbye.  _ Dean smiles softly, his eyes are tired but the happiness in them is genuine. Dean’s fingers fall away from Cas’s chin, his smile fading.  _ I’m sorry this is the last thing you’ll remember of me. But I guess it makes quite a story huh?  _ Cas can’t force himself to smile, in fact he can’t help the frown that twists his lips.

Dean’s expression mimics his own and they both stare at each other, hovering but a few mere inches from each other. There is a heavy tension between them, Cas can feel it burning his limbs as Dean’s eyes scan him. He’s trying to memorize what I look like, Cas realizes, but that doesn’t seem to be the only reason.

Dean swallows and Cas can see him composing himself, a mask falling over his face.  _ I guess you’re free now… You aren’t trapped in this old cave anymore. I… I hope you have a good life and— _

_ Stop.  _ Cas squeezes his eyes shut and shakes his head.  _ Just stop… _

_ Why?  _ Dean asks, keeping his voice calm.

_ Because.  _ Cas can’t take it anymore.  _ I—I don’t want to go. _

There is a sharp intake of breath, and Cas risks a look at Dean to see the selachii tensed.  _ You don’t mean that. _

_ Yes,  _ Cas admits,  _ Yes I do. Where would I go Dean? I have  _ ** _nothing _ ** _ to go back to! _

_ Is that the only reason?  _ Dean says suddenly, his voice taught. Cas stares into his emerald eyes. The light from the crystals reflects in them, making them glisten even more than usual. Dean’s eyebrows are raised in question and as best as Dean tries to hide it, Cas sees through his mask, the hard stone faced shell he’s putting on. It’s the same fear, the same hesitation he himself feels reflected back at him.

Cas swallows,  _ No… _

There’s a spark in that green, a flame flickering with hope. Dean swims ever so slightly forward.  _ Are—Are you sure?  _ Dean licks his lips.

_ Yes,  _ Cas nods confidently.

Dean rubs his jaw nervously,  _ Y-you want to— _

_ Yes,  _ Cas exhales in exasperation and shoots forward, throwing caution to the current.

They meet halfway, lips locking as they embrace each other. It shocks Cas like a stream of cold water, sparking his senses and setting his heart racing. They aren’t even moving, just a soft but firm press of lips against lips and he’s hooked. Then, very slowly, Cas feels Dean start to move. He leans out briefly, hands firm on Cas’s arms and eyes hesitantly meeting his. It’s one last question, one chance of backing out—but Cas doesn’t want it.

A smirk curves Dean’s lips and Cas feels himself doing the same. Dean presses in again, this time kissing Castiel with confidence and vigor. They’re both slow, relishing the moment and being careful not to hurt the other. Finally, they’re both confident enough to slide their tongues against each other, carefully teasing with sharp teeth.

Cas has felt nothing like this before. Having only tried to mate once before with no success, this was completely new. Everything was unfamiliar, the tilt of Dean’s head, the precision of his movements and the shape of his body. But Cas wanted to learn and explore, map out the plane of his physique and commit it to memory. He doesn’t want to let go of this.

Cas pulls away reluctantly, cupping Dean’s cheek and looking him square in the face.  _ Dean…  _ he tries to pull Dean back to reality for a moment, he knows how easy it would be to just let go and let this happen. But there was a future to think about. _ I need to know if you want this. I mean really want this… because—what do we do after this? I—I can’t come with you Dean. _

_ Says who? _

Cas frowns,  _ I thought… you said. _

_ I only kept pushing you to leave because I thought that’s what you wanted. But— _ Dean’s smile brightens.  _ But you want to stay now. And I want you to stay. You can come with me Cas. _

_ What about Sam?  _ Cas inquires.

_ Sam will be fine. I’ll introduce you to him. _

_ But wouldn’t he be afraid of me? _

Dean laughs,  _ You? No. Cas, my brother is about as open-minded as it gets. And knowing you’re with me, you’ll fit right in. _

Cas’s eyes widen.  _ But wouldn’t I burden you? Having another mouth to feed. _

Dean shakes his head.  _ We work together Cas. Whatever rules your cecaelia society burned into your brain, you don’t need to worry about them anymore. You’re not weak or soft—or whatever else they called you. You’re amazing, Cas.  _ Dean cups Cas’s face in his hands.  _ The ocean is a huge and wondrous place. What are the chances that we got to meet? This— _ Dean places a hand on Cas’s chest,  _ is a miracle. _

Cas feels his eyes burning, his face crumbling. After his exile, there should’ve been nothing left for him. He should’ve died forsaken and disgraced. Yet here he was with a light shining in his future if he let it, because of Dean.

_ Oh Dean.  _ Cas places a hand on Dean’s where it lays over his heart.  _ You’ve already done so much for me. I can’t ask you to do this. _

_ But I want to.  _ Dean leans in and presses a kiss to his forehead.  _ What do you say? Wanna come on a new adventure with me? _

Cas doesn't know how to express the gratitude he feels. There are no words for the gifts Dean has given him. Finally, Cas decides on resting his head on Dean’s shoulder, snuggling into his neck, breathing in his scent.  _ I… I’d love that Dean.  _ Cas feels Dean swallow then slowly wrap his arms around his back and pull him closer.

_ Good…  _ The smile Cas feels against his skin is radiant.

Castiel slides his other arms around him in return, his tentacles tenderly wrapping around Dean’s tail with soft kisses. Dean sighs as Cas settles around him, stroking his skin lovingly with hands and arms. Cas leans back slowly, his eyes shining.  _ Thank you, Dean. For everything. _

Dean leans back in, eyes half-lidded.  _ And thank you… for coming into my life.  _ He kisses Cas again, eyes slipping closed and capturing the cecaelia with his lips. Dean presses in again and this time Cas is surprised to hear himself groan, a deep burning bubbling its way up to his gut. He knows what it means, an excitement rushing through him.

Dean smiles into the kiss as he pulls another noise from Cas, making his tentacles curl tighter around him. When he pulls back, Cas is breathless.

Castiel stares at him wide-eyed, eyes dark and almost glowing.  _ Are we really doing this? _

Dean smirks, a satisfied grin on his face.  _ Only if you want to, cuttlefish. _

_ Hell yes.  _ Cas pulls Dean down by the back of his neck, smoothly rolling them so Cas could grasp the floor with two arms and pillow Dean below him with the others, keeping Dean’s injuries in mind.

Dean gasps as Cas pins him to the ground. Cas freezes.  _ Did I hurt you? _

_ No,  _ Dean chuckles,  _ just pleasantly surprised. Don’t worry about me, I’ll tell you if something hurts. _

_ Okay.  _ Cas nods, eager but nervous.

_ Come on, you’re fine.  _ Dean smiles at him when the pause goes on too long, sweeping his tail lazily.  _ You had it right the first time you had me like this,  _ he teases. Dean raises his hands above him, tipping his head to expose his gills in a vulnerable position. Cas understands the pose immediately and quickly moves a tentacle from Dean’s body to around his wrists, securing him in place. Dean flexes against them but can’t move however hard he tries. It gives Cas some satisfaction, knowing Dean has given him the upper hand here.

Instinct begins to buzz in Cas’s body. Though unpracticed there is a deep lust that fills and guides him, twitching at his fingertips and rippling across his skin in shimmers of red and blue. The display catches Dean’s eye. Cas watches with satisfaction as Dean’s pupils widen, the fluctuating colors reflecting on his skin.

Dean continues to stare and Castiel takes the opportunity to observe Dean’s body properly. Dean’s ribs are bruised but the roll of his muscle is unmistakably alluring. His eyes wander further down until he sees a slit below Dean’s navel, where his torso merges with his tail. Cas isn’t a stranger to other creature’s anatomy, he’s educated himself after all, and he smiles knowingly.

Cas bends down over Dean, snapping the selachii’s eyes back to his own. He latches onto Dean’s neck, mouthing at the skin behind his gills, scraping lightly with his teeth. Dean’s breath hitches, exhaling heavily into his hair. Cas drags his hands down Dean’s body slowly, scraping over his nipples all the way down to his hips, grasping him there. Dean squirms the entire time, tail twitching as Cas’s tentacles begin to tighten and suck at his skin, constantly moving and touching all within their reach. With Dean’s hips secured, Cas makes his way down with his mouth, nipping lightly at the smooth skin and softly kissing the injured portions.

Dean does nothing but watch with fascination until Cas finally looks up to him, a smirk on his face. Castiel replaces his hands’ grip with a strong arm around Dean’s waist, lowering his head and hands to Dean’s bottom half. With one last glance up at Dean, Cas lowers his gaze to Dean’s slit and drags his tongue across the protruding skin.

Dean moans at the warmth of Cas’s lips, the cecaelia mouthing at his vent and smiling as he feels a bulge growing beneath the skin. Cas begins to tease the slit with his tongue and feels a dose of satisfaction when Dean groans loudly and bucks against his restraints. Cas persists, pressing with his tongue until the vent finally gives way and he plunges in. Dean cries out as Cas twirls his tongue and slides across the head of his cock hidden inside. Cas sucks insistently, encouraging the cock into his mouth.

_ Holy fuck,  _ Dean pants in surprise,  _ Where the hell did you learn that?  _ He whines as Cas sucks again, his dick finally pressing at the back of the cecaelia’s throat.

Cas chuckles as his mouth is currently occupied. He begins to bob up and down, licking up and down Dean’s shaft and playing with the spine underneath. Dean is squirming even more now, his hips pressing forward and his voice cracking through the water. Still, Cas does not let him go.

Castiel slowly rises off of his cock, simultaneously wrapping a tentacle around him as he pulls off until he’s fully wrapped around him, squeezing and kissing with more pressure than before.

_ AH!  _ Dean screams at the tentacle squeezes around his dick and Cas suddenly surges upward with all his arms, hands and mouth. He snares Dean’s mouth, capturing the noise and devouring it. His arms move quickly and without mercy, no longer securing them to the floor, they float suspended, the cecaelia using all his tentacles, one playing with Dean’s nipple, one constantly moving across Dean’s writhing torso, one rubbing across his tail, another diving deeper into his vent, and the last one not at his dick or wrists encircling his throat.

Dean is helpless, paralyzed as he’s smothered in a blanket of velvety arms burning arousal into his veins and choking him with bliss.

Finally Cas releases Dean’s wrists but Dean is too overwhelmed to realize it until Cas breaks the kiss. He can do nothing but stare in wonder as Cas bites at his neck, grabbing Dean’s hands with his own and squeezing them tight. Dean grasps his hands just as tight, warmth bleeding through him as the intimate gesture softens the brutality of their love-making.

The free tentacle slides across Dean’s face, kissing his skin as it passes over his cheek, sliding down his chest to play with his other nipple.

Dean groans, breathing heavily as his senses are overwhelmed. The arm around his neck loosens to let him breath and slides up to stroke his cheek lovingly. With a harder squeeze around his dick Dean’s head lolls back, mouth open. He’s only slightly aware of a hand cradling his head, tilting it back for Cas to better mouth at his neck.

_ Is this what you want?  _ Castiel’s voice rumbles against his gills. Dean shivers harder than before, writhing and gasping, unable to answer the cecaelia’s question.

The pain in his body is long forgotten, his wounds replaced by bright blue eyes and a warm, firm embrace.  _ Yes—yes,  _ Dean manages to whimper. Cas hums with satisfaction.

_ Say my name,  _ Cas hisses into his ear.

_ Cas. _

_ Again. _

_ Cas!  _ The arms around Dean squeeze ever tighter, building the pressure burning in his gut and buzzing every nerve on his skin.

Cas’s hands combs through his hair, and Dean forces his eyes to focus. Cas scans his face with a loving smile,  _ Let me take care of you. You’ve taken such good care of me. You saved my life— _

_ And you saved mine,  _ Dean replied, using his now free hands to cup Cas’s face,  _ Let me love you too.  _ He trails a hand down to explore the vast expanse of Cas’s muscular torso. Still tied up in tentacles, with some difficulty Dean looks down to look for any hint of genitalia on the cecaelia. He frowns when he realizes he sees none.

Cas chuckles when he sees the puzzled look on Dean’s face.  _ My genitalia are not unlike your own—just in a more hidden spot.  _ Cas takes the hand on his torso and leads it downwards. Dean goes wide-eyed when Cas guides him under the strong arms still gripping him. He can see nothing but when his hand touches skin he gasps. Hidden somewhere under the mass of arms is a clear and very stimulated cock. Cas releases his wrist and Dean takes the invitation to wrap his hand around the thick length. Castiel immediately convulses, a groan pouring from his mouth as he arms flex and ripple a deeper shade of red.

_ Agh!  _ Dean’s surprise is heightened as the arms around his, well—everything, squeeze harder then ever before. He could cry from the stimulation on his poor cock or from the fact that breathing is now very difficult.

Dean rips his hand from Cas’s face and tries to push at the arm around his waist.  _ Hey—Cas! _

Dean almost laughs at the way Cas’s face changes from pure bliss to startled confusion then horrified realization.

_ Oh gods I’m sorry!  _ Cas releases Dean, much to the selachii’s disappointment.

Dean takes a deep breath through his gills.  _ No Cas it’s okay, it was kinda funny and sorta hot actually. Just remember I need to breathe. Now come on, what else can you do with those arms? _

Dean rolls his eyes as Cas still looks slightly mortified. He swims to him, surging towards him with a deep kiss and letting his hand slide back down under his array of tentacles. Dean’s first touch of Cas’s cock earns him a moan that he swallows from Cas’s mouth.  _ Please,  _ Dean whines,  _ Touch me again, please. _

Dean can see the building of animalistic hunger in Cas’s eyes, the predatory glow and twitching of tentacles. Dean leans in close, stroking the cock in his hand.  _ Touch me again.  _ A low growl builds in Cas’s throat, Dean smiling at the obvious desire. He decides to push just a little more.  _ I’m all yours. No one else's. Make me yours and I’ll make you mine.  _ Dean drags his tongue down Cas’s neck until he reaches his shoulder. He scrapes his sharp teeth over the spot, biting lightly. As Dean suspected, Cas’s arms fly back around him, this time squishing them together but with tentacles still in all the right places. Dean cries out when he feels Cas take up the same position on his shoulder.

_ Mark me Cas, please. _

Cas is panting, Dean continuing to stroke Cas faster and faster.  _ I’ll bear your scar and you’ll bear mine.  _ Dean nods wordlessly, their conjoined forms twirling in the cavern’s water.

They both tense, waiting for the right moment, the heat in their bodies building and building until it is unbearable.

_ Dean,  _ Cas’s wrecked voice was the tipping point. With one last squeeze of Cas’s tentacle, Dean is spilling, his scent filling the water around them. He bites down, moaning as his teeth pierce flesh. Cas’s arms explode in a rainbow of color as he soon follows, moaning unapologetically as he too sinks his teeth into Dean’s shoulder.

They ride their high together, panting into each other's skin as the smell of their seed begins to fill the water. Dean is the first to let go, withdrawing his fangs and falling against the cecaelia’s chest. Cas slowly follows, Dean wincing slightly. The pain soon fades when Castiel hugs Dean closer, allowing them to both sink slowly to the cavern floor as Cas mouths over the bite, licking it clean with his tongue. With eyes half closed and body loose, Dean just remembers to return the favor. His movements are slow, lethargic. But he wants to take his time, the fuzzy glow in his mind makes Cas taste even sweeter.

By the time they hit the bottom, their marks are clean, matching bites burning red and bright, a physical brand of their devotion. Both sigh as they lay on the soft moss, Dean snuggling closer and letting Cas’s arms once again surround him. But they move lazily now, lying atop him like a blanket. Dean breathes him in and Cas does the same. A warmth, softer and lighter than before simmers in their chests, an eternal flame.

It’s so very tempting for Dean to slip off into sleep but there are things he wants to say and a few things he should probably do.  _ Cas…  _ he murmurs into the cecaelia’s skin.

_ Yes, Dean?  _ His low voice hums in Dean’s ears.

_ Besides Sam, you’re the best thing that’s ever happened to me.  _ It might be sappy, but it’s true.

Dean feels Cas smile against his neck.  _ The feeling is mutual. _

_ Good.  _ Dean smiles back.  _ Hey…  _ He pulls back enough to look into Cas’s eyes.  _ You’re still coming back with me. _

Cas huffs,  _ I know. _

_ Just making sure,  _ Dean smirks, _ You’re gonna love Sam. He loves learning and exploring, you two will get along just fine. Though, fair warning, he’s probably gonna ask you a million questions about cecaelia stuff. _

Cas chuckles,  _ You mean just like you did. _

Dean rolls his eyes,  _ Yes, just like I did, just more Sam-ly. _

Cas shakes his head,  _ I don’t think I’ve ever been this happy…  _ He shuffles closer, tightening his arm around Dean’s torso.

Dean smiles softly, quiet as he looks down at the cecaelia.  _ Yeah…  _ He kisses the top of his head.  _ Me neither. _

They stay for a moment longer, comfortably silent, basking in each other’s presence. It’s only when Cas says,  _ It’s nightfall,  _ that Dean forces himself back to reality.

He sighs,  _ Sam’s probably worried sick. We should head back soon.  _ Cas hums in agreement but neither of them move.

Dean chuckles again,  _ Just a while longer?  _ Cas doesn’t answer, simply snuggles against his neck with a smile.  _ Alright then… a bit longer. _

They lay for a while, exactly how long they don’t know. This is their moment, one neither of them would forget for as long as they live. It’s burned into their memories and etched in their flesh. They are intertwined, inseparable, as it should always be.

When they finally swim out of the cave, hand in hand, neither of them look back. Dean leads him above the trench, across the open ocean, never once wavering or questioning. Cas is family now, his family, and he will never let him go.

Their home comes into view and Dean delights in the smile on Cas’s face. It’d be a long story, but he knows Sam will understand.

With a kiss to Cas’s cheek and joy in his voice, he says,  _ Welcome home. _

**Notes for the Chapter:**

> Aaaand tada! That's it! :D Cas gets to join Sam and Dean on their own adventures across the ocean blue <3 He has a real family now and a lover who will always care for him. I hope you enjoyed this short story. I'd been sitting on it for a while but I'm glad I've finally gotten it out there. Thanks to all of you who have read, kudos'd, and commented <3 every one of you is appreciated! I hope you all have a good night, morning, or whatever time left of your day there is lol


End file.
